A hybrid vehicle may be provided with a driveline disconnect clutch. The driveline disconnect clutch may be closed to couple an engine with an electric machine. The driveline disconnect clutch may be opened to decouple the engine from the electric machine. The engine may provide torque to the driveline when the driveline disconnect clutch is closed. The engine is stopped when the driveline disconnect clutch is open to conserve fuel. However, if a driver increases a driver demand torque when the engine is stopped, it may take an objectionable amount of time to restart the engine and provide engine torque to the driveline.
The inventors herein have recognized the above-mentioned disadvantages and have developed a driveline operating method, comprising: operating an engine and providing engine torque to a driveline propelling a vehicle in response to a desired torque being greater than a threshold driveline integrated starter/generator torque; and operating the engine and not providing engine torque to the driveline in response to the desired torque being less than the threshold driveline torque and greater than a threshold engine cranking torque.
By defining during which vehicle conditions an engine operates in a sailing mode, it may be possible to improve torque response of a vehicle driveline. For example, an engine may be operated in a sailing mode, where the engine idles at fuel efficient operating conditions, when a driveline torque is less than a threshold driveline torque (e.g., a torque capacity of a driveline integrated starter/generator (DISG)) and when the driveline torque is greater than a threshold engine cranking torque. Thus, when the vehicle operates with a middle level driver demand torque, the engine may be operated in a fuel efficient torque responsive mode. If the driveline torque demand increases, engine torque is available to the driveline via closing the driveline disconnect clutch. If the driveline torque demand decreases, the engine may be stopped to provide decreased fuel consumption.
The present description may provide several advantages. Specifically, the approach may improve driveline torque response. Additionally, the approach may improve vehicle drivability.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.